Electrokinetic characteristics of particulate/liquid interfaces and their importance in contamination from semiconductor process liquids.

Abstract

Particulate contamination during wafer processing is a major concern in the microelectronics industry. The impurities may be generated from holding tanks, shipping containers, filter membranes and photolithographic materials, and hence may be organic and inorganic in nature. In liquids, these particles develop a surface charge, the magnitude and sign of which is unique for a particular solid/liquid combination. The substrate that is processed in liquids also develops a similar surface charge, and if the charge on the substrate and impurity particles are opposite to each other, deposition of impurities onto the substrate is likely to occur. Hence an understanding of the surface charge characteristics may have an impact in developing techniques to control particulate contamination from semiconductor process liquids. In this work, an attempt has been made to elucidate the surface charge characteristics of a variety of organic and inorganic particles in liquids of interest to the semiconductor industry. The techniques of microelectrophoresis and streaming potential using flat plates and filter membranes were used to this end. The data obtained have been utilized to understand and predict particulate contamination from liquids and deposition onto the wafer surfaces. This might in turn be useful in developing filter membranes of interest to the semiconductor industry.